1. Technical Field
The present invention relates to an inkjet printing method for forming a continuous three-dimensional structure, especially relates to an inkjet printing method for forming a continuous three-dimensional structure by a self-aligned effect.
2. Description of Related Art
Photolithography process is a key step in manufacturing the semiconductor devices. A conventional photolithography process mainly includes: photoresist coating, exposure, and developing. First, a photoresist is deposited on a substrate, and then an exposure process through a pre-patterned mask is performed on the photoresist. Finally, a developing process is performed to remove the unnecessary part of the photoresist, and a patterned photoresist is formed. The conventional photolithography process is complicated and requires expensive materials and equipment, so that leads to a decrease of the manufacturing yield and a waste of cost.
Recently, wide researches are performed on finding simpler processes that can replace the photolithography process, and an inkjet printing process is a rapidly developed technology to replace the complicated photolithography process. A conventional inkjet printing process is used for generating patterns on a substrate. When a pressure generated from the phase transition of an ink droplet or a nozzle is larger than the surface tension of the ink droplet itself, the ink droplets are purged to a substrate and a pattern is formed. In the inkjet printing process, the characteristics of the ink droplet are very important. The parameters of the ink droplet such as inertia, viscosity and surface tension should be taken into consideration. In sum of all, like the photolithography process, the purpose of the inkjet printing process is also to form a pattern on a substrate. Compared to the photolithography process, the inkjet printing process has advantages on simpler process and cheaper equipment, thus a low cost of the manufacturing is obtained, and the manufacturing efficiency is enhanced.
However, there exist disadvantages on the inkjet printing process. First, the uncontrollability of the ink droplets track leads to defects occurred on the formed pattern. Second, the characteristic of omnidirectional flow of the ink droplet leads to constrains on resolution of the formed pattern. The issues above make it difficult on applying the inkjet printing process to a structure with a small track width (e.g. <10 μm) or with complicated network geometry. In most case, the structure is more complicated, thus limit the capability of the inkjet printing process. Furthermore, if apply a nozzle with smaller diameter for reducing the track width, the incompatibility of the ink droplet will occur. This is due to the ink droplet contain nano-particle suspensions, and the probability of nozzle blocking will increase with the decrease of the diameter of the nozzle.